Dr. Jeff Hersh: Debunking medical myths

Tuesday

Sep 20, 2011 at 12:01 AMSep 20, 2011 at 7:15 PM

Friends, relatives and even our health care providers have all, over the years, spouted certain "medical facts" we question. Today I will discuss some of these, based on the best information I could find.

Dr. Jeff Hersh

Friends, relatives and even our health care providers have all, over the years, spouted certain "medical facts" we question. I will discuss which of these are facts and which are myths based on the best information I could find.

Knuckle cracking will lead to arthritis: False.

When the bones that meet at a joint move in a certain way, the space between them may increase, causing the synovial fluid, which is the lubricating fluid in our joints, to spread out to fill the larger volume. The associated decrease in pressure when this happens can cause a relative vacuum, which makes some of the dissolved gases in the fluid (mostly nitrogen) to form into bubbles. As these bubbles burst, the knuckle "cracks."

There are many different types of arthritis, which in general is an inflammatory condition. It can be caused by an autoimmune reaction –– the body's own immune system inappropriately attacking itself, such as in rheumatoid arthritis; build up of crystalline deposits, such as from gout; wear and tear of the cartilages, as in osteoarthritis; infection in the joints, from Lyme disease, for example; as well as other causes. Although constant knuckle cracking may theoretically be able to injure the joints to some mild extent, it has not been shown to cause arthritis, even osteoarthritis.

If you swallow gum it stays inside you for years: False.

Gum is not digestible, meaning our digestive enzymes are not able to break it down to extract its nutrients. This simply means that the gum will pass through the digestive tract like any other indigestible substance that has been eaten. This typically takes two to three days, not years.

Finger nails and hair grow after death: False.

After someone dies, the skin and other body tissues dry out, retracting as they do. This can make it appear that their nails and/or hair are growing, but the body tissues do not grow after death.

The color of your urine changes if you are dehydrated: True.

Clearance of certain substances by the kidneys can cause the color of urine to change. This may occur after eating certain foods. For example, eating lots of carrots can cause urine to have an orange hue and beets can cause it to be reddish. This may also occur after taking certain medications. Blood in the urine, which can occur from many conditions, can also change the urine's color.

However, the most common cause of a change in the color of someone's urine is changes in the concentration of water in their urine. Under control by hormonal signals stimulated by the body's fluid status, such as dehydration, and other factors, such as one’s electrolyte balance, the kidneys have remarkable control over how concentrated the urine is ––typically within a range of random urine osmolality, a measure of urine concentration, from 50 to 1400 mOsm/Kg. Dilute urine will look light yellow or even clear, while very concentrated urine will appear dark yellow. So dehydration is one of the things that can change the color of someone's urine.

Going out in the cold can make you catch a cold: False.

The "common cold" is an infectious disease; many hundreds of different viruses can cause it, but just being out in the cold does not cause it. In fact, the reason people get colds more often in the winter is that they huddle together inside where it is warm, spreading cold viruses by coughing or sneezing on each other, or by touching surfaces on which any virus they have can be transferred to someone else.

Eating chocolate causes pimples: False.

Acne is caused by blockage of a hair follicle, causing oil and cellular debris to collect under the skin. This leads to swelling and inflammation. Certain bacteria that normally live in the skin by the base of the hair follicles, hormonal influences and other factors may contribute to this inflammatory condition. However, eating chocolate or other foods, even fried foods, has not been shown to be associated with acne.

Reading in poor light can strain your eyes: True.

When you read in poor light, your eye muscles must work hard to keep what you are reading in focus, eventually causing strain. However, reading in poor light does not lead to permanent eye problems.